$K_L \ra μ^\pm e^\mp ν\overlineν$ as background to $K_L \ra μ^\pm e^\mp$

Abstract

We consider the process $K_L \ra μ^\pm e^\mp ν\overlineν$ at next to leading order in chiral perturbation theory. This process occurs in the standard model at second order in the weak interaction and constitutes a potential background in searches for new physics through the modes $K_L \ra μ^\pm e^\mp$. We find that the same cut, $M_{μe}>489$~MeV, used to remove the sequential decays $K_{l3}\ra π_{l2}$ pushes the $B(K_L \ra μ^\pm e^\mp ν\overlineν)$ to the $10^{-23}$ level, effectively removing it as a background.